Swivel-type casters have been provided in industrial environments for many years to movably support a variety of equipment, such as material handling carts and work tables. Frequently this type of swivel caster includes a pintle which is an upwardly extending shaft that fits through a complementary female recess in the equipment to be supported. The pintle absorbs the bending loads placed on the caster assembly by the supported equipment.
Some swivel casters are pintleless in the sense that the caster is attached to the supporting equipment by fastening a swivel plate directly to the equipment being supported. In this case the swivel plate itself absorbs the torque loads applied by the equipment to the caster assembly. Such a design has the disadvantage that the fasteners connecting the swivel plate to the supported equipment are under very high loads and also the strength of the swivel plate limits the caster's load capacity. The addition of a pintle not only permits easier removal of the caster assembly from the supported equipment more readily than the swivel plate attachment type, but also increases overall caster strength since the pintle absorbs a significant portion of the bending loads applied to the caster by the supported equipment.
The most difficult problem in these pintle and swivel plate type casters is mounting the pintle in a way to resist bending loads to minimize bending and breaking of the pintle. One attempt to solve this problem has been to provide a bottom plate underneath the horn to which the end of the pintle is staked. In this arrangement the pintle is radially supported at two spaced locations, one in a central aperture in the swivel plate, and the other in a through bore in the bottom plate. However, since the bottom plate is usually radially supported by roller bearings there is no rigid radial support provided by the bottom plate and hence the single aperture in the swivel plate, which is a relatively thin member, has frequently been found to be inadequate to withstand the bending forces applied by the equipment to the pintle and the pintle fails.
Another problem in the pintle-swivel plate type caster is that sometimes the pintle itself is bent slightly during formation and cannot be straightened during assembly into the caster and thus must be rejected.
It is the primary object of the present invention to ameliorate the problems noted above in heavy-duty swivel type casters.